The efficiency of light-emitting devices based on nitride compound semiconductors is dependent on how effectively charge carriers can be injected into the active layer and confined therein. If not all the charge carriers recombine in the active layer, but rather are lost in other regions of the semiconductor device, efficiency decreases. In particular the lasing threshold and the steepness of the characteristic curve of semiconductor lasers based on nitride compound semiconductors are dependent on charge carrier injection efficiency.
In order effectively to capture electrons in the active layer of a light-emitting device based on a nitride compound semiconductor, a p-doped electron barrier layer adjoining the active layer may be used, which generally has a comparatively high aluminum content of up to thirty per cent. It has however been demonstrated that a conventional electron barrier layer generates strong piezoelectric fields due to the great lattice mismatch between the electron barrier layer and the surrounding semiconductor material. The piezoelectric fields bring about local deformation of the band structure, which leads to the formation of band edge minima in the region of the electron barrier layer. For this reason, high electron and hole densities may arise there, which may lead to optical losses.